1. Field of the Invention
The present invention relates to a non-contact power supply apparatus which supplies power to electronic equipment containing a charging battery by electromagnetic induction without contact.
2. Description of the Related Arts
Hitherto, methods for supplying power by electromagnetic induction were disclosed, for example, in Japanese Non-examined Patent Publication No. 3-98432. The structure of the apparatus used in this method is as shown in FIG. 5.
That is, this apparatus has separately provided on its supply side a supplying oscillating circuit 6 in which a supplying oscillating coil L6 is connected to an oscillator B3, and a supplying resonance circuit 7 in which a resonance capacitor C6 is connected in parallel with a resonance coil L7.
In addition, this apparatus has on its receiving side a receiving resonance circuit 8, in which a receiving resonance capacitor C7 is connected to a receiving resonance coil L8, and a rectifier smoothing circuit 9 containing a bridge D3 and a capacitor C8.
Further, the disclosed apparatus is capable of transmitting power efficiently by causing supplying oscillating circuit 6 to oscillate at a predetermined frequency approaching the resonant frequency of supplying resonance circuit 7 and receiving resonance circuit 8, so that it virtually resonates at the frequency of supplying oscillating circuit 6, supplying resonance circuit 7, and receiving resonance circuit 8.
However, in the above-described type of apparatus the resonant frequency of supplying resonance circuit 7 and receiving resonance circuit 8 is independently determined. The oscillating frequency of supplying oscillating circuit is also fixed independently.
For this reason, a change in load at the receiving side changes the resonant frequency of the resonance circuit 8 at the receiving side, preventing tuning of oscillating circuit 6 and resonance circuit 7 on the supply side with resonance circuit 8 on the receiving side. Consequently, the amount of power which can be supplied is greatly reduced, and sufficient power cannot be stably supplied.